1. Field of the invention
This invention relates to a data filtering method, and more particularly, to the data filtering method for filtering a 3G data stream which is received. The data filtering method effectively promotes the ability of processing invalid data of the receiving end of telecommunication, so as to promote the video/audio effects and keep the communication quality higher when the Internet is unstable or the system is running at high load.
2. Description of the Related Art
With the progress of technology, the functions of hardware and software of cell phones have become stronger, so the media functions of the cell phones become more diverse. Nowadays, users can take pictures, listen to music, or watch movies via cell phones. As having been noted, users at two ends in communication could only transmit voices or messages via cell phones in the past. Compared with the delivery of voices, the delivery of images needs larger bandwidth. So, larger network bandwidth is needed to perform video communication smoothly. Until now, the mobile communication network of cell phones has moved forward from 2G era to 3G era, even to 4G era in the future, so the bandwidth of mobile communication network will be much wider and bear the video streams whose requirements of bandwidth are larger. So far, users can acquire the function of video communication through a 3G cell phone. That is to say, the users can see the images and hear the voices of the other side, such as the video conference. Because a common 3G cell phone has a video lens, the dynamic images of users can be captured through the video lens and delivered to the other side via the 3G network, so that the cell phone of the other side can display the dynamic images.
The foregoing 3G-324M protocol is a complex protocol, established after collecting many protocols and being revised by an international group: 3rd Generation Partnership Project (3GPP). Besides, it mainly includes many protocols consisting of H.324, H.223, and H.245, and each protocol accomplishes specific functions. Please refer to FIG. 1. FIG. 1 is an infrastructure diagram illustrating the receiving end 1 of a video phone in the prior art. The video phone in the prior art mainly includes a 3G network layer 12, a device driver adaptation layer 14, a 3G-324M protocol 16, and a video phone application layer 18. The 3G-324M protocol 16 mainly includes H.223 protocol 162, H.245 protocol 164, and H.324 protocol 166. Wherein, the H.233 protocol 162 includes a multiplexing/demultiplexing layer 1622 and an adaptation layer 1624. In a word, the functions of the H.223 protocol 162 are multiplexing/demultiplexing and debugging the data in protocol layers. Wherein, the function of multiplexing/demultiplexing is dominated by the multiplex/demultiplex layer 1622, and the adaptation layer 1624 is used to provide the functions such as error code controlling, error code checking, and series numbering mechanism. The function of the H.245 protocol 164 is the processing of control signals.
Before the H.324 protocol of the video phone works, a transmission channel of the bit rate of 64K bit/s will be built in 3G network firstly. Once the transmission is built, the H.324 protocol starts to work. When there is no audio/video signal and control data needs to be transmitted, the H.324 protocol will transmit constant filling codes to the receiving end. In general, the filling codes are all invalid data representing one or more of the number of zero (hereinafter called “zero data”). In other words, when the 3G-234M protocol of the video phone is in the situation of rest, the system will receive the data stream full of zero. Please refer to FIG. 2. FIG. 2 is an image illustrating the bit stream data of a video phone in the prior art. When the 3G-324M protocol of the video phone starts to work, the received data (e.g., video data and audio data) will include the constant data unit defined by the 3G-324M protocol, such as the data unit which begins with “E1 4D 00 00 00” shown in FIG. 2. If the handshaking procedure had been performed, control signals or video, audio and data will be filled among the constant data units in accordance with the 3G-324M protocol. Contrarily, when the 3G-324M protocol of the video phone is in the situation of not receiving control signals, video data or audio signal, the system will fill zero data among constant data units to keep the constant bit rate of 64K bit/s.
Generally, when the receiving end in communication receives bit stream data, the original method is to directly transmit the data stream received by a modem to the 3G-324M protocol to process, to analyze the data stream by the 3G-324M protocol according to its protocol specification, and to feedback the processed result to the application programs. If sending data in constant 64K bit/s data rate under the situations that the network signals are weak or other tasks which consume resources are simultaneously performed while communicating with a mobile phone, the data streams which are shown in FIG. 2 will occur instantly or intermittently. As shown in FIG. 2, it is obvious that there are numerous zero data filled among the bit stream data. Those zero data are filled by the Internet layer for keeping the filling data rate of 64K bit/s. But the fact also proves that the data will make the 3G-324M protocol to analyze and process incorrectly.
However, during the use of a video phone, a user will find that the quality of communication at the receiving end will be effectively affected in the situations when the network signals are not strong enough or other application programs (e.g., some functions which consume the resources of the CPU, such as transmitting-receiving multimedia mails, playing mp3, taking photos, playing games, etc.) are performed simultaneously while proceeding video communication at the receiving end. For example, the situations will generate the phenomenon such as the blocks or mosaic in video images, the noises in audio signals, etc. The situations that error code data are generated are due to the weak network signals. Moreover, the most important reason of the foregoing situations can be discovered by analyzing the retrieved data that the received data are filled numerous invalid data at network terminal. However, the present 3G-324M protocol of the video phone cannot effectively process the invalid data. Namely, if the invalid data are regarded as valid data, the following decoder programs will not efficiently analyze the original video/audio contents.